In telecommunications networks that support mobile subscribers, there is a need to know or determine the current location of mobile subscribers so that calls, emails, short message service messages, or other data may be communicated to those mobile subscribers. In mobile telephone networks, there are network entities, usually servers, which maintain that information. These network entities may receive queries for the current location of a particular mobile subscriber, and may reply with the current or last known location of the mobile subscriber. The location is typically given in the form of the network address or ID of a switch, such as a mobile switching center (MSC), that is currently serving the mobile subscriber.
In second-generation (2G) telecommunications networks, the entity that manages this information is called a home location register, or HLR. In third-generation (3G) telecommunications networks, the entity that manages this information is called a home subscriber server, or HSS. Networks that use the session initiation protocol (SIP), such as Internet protocol multimedia subsystem (IMS) networks, also include an HSS.
FIG. 1 is a block diagram illustrating an IMS network. Network 100 includes an interrogation call session control function node, I-CSCF 102, which processes SIP messages and routes subscriber-related messages to the correct serving call session control function node, or S-CSCF. Network 100 has four S-CSCF nodes, 104A, 104B, 104C, and 104D, which hereinafter may be collectively referred to as S-CSCFs 104. Each S-CSCF 104 serves a subset of the subscribers within network 100. S-CSCFs 104 provide services for the subscribers, such as setting up media communication sessions between subscribers and applications.
Network 100 also includes an HSS 106, which contains subscription-related information, such as user profiles, performs authentication and authorization of subscribers, and can provide information about the physical location of the subscriber.
In the network illustrated in FIG. 1, I-CSCF 102 receives a SIP INVITE message 108. SIP INVITE message 108 may request a communication session with a particular subscriber, herein referred to as the called party, or CDP. To determine the current location of called party subscriber CDP, I-CSCF 102 queries HSS 106 by sending a Diameter protocol location information request (LIR) 110. HSS 106 responds with a Diameter location information answer (LIA) 112, which identifies the switch that is currently serving called party subscriber CDP. In the example illustrated in FIG. 1, HSS 106 may indicate to I-CSCF 102 that called party subscriber CDP is currently served by S-CSCF 104C, in which case I-CSCF 102 will forward the SIP INVITE message to S-CSCF 104C, shown as SIP INVITE message 114.
As the number of subscribers in a network increase, however, it may be necessary to distribute the HSS functions across more than one HSS node. FIG. 2 shows an example of such a network configuration.
FIG. 2 is a block diagram illustrating an IMS network having multiple HSS nodes. IMS network 200 includes an I-CSCF 202 for processing SIP messages and routing subscriber-related messages to the appropriate switch, such as S-CSCF nodes 204A and 204B, which hereinafter may be collectively referred to as switches 204 or C-CSCFs 204.
Network 200, however, includes multiple HSS nodes, HSS1 206A and HSS2 206B, which hereinafter may be collectively referred to as HSS nodes 206, across which is distributed subscriber information. In order for I-CSCF 202 to determine which HSS node 206 to query, network 200 includes a subscriber location function node (SLF) 208. In the network illustrated in FIG. 2, SLF 208 maintains an SLF table 210 for mapping subscribers to HSS nodes. SLF table 210 contains multiple rows, each row representing an entry in the table. Each entry maps a subscriber ID, shown in the left column of each row, to an HSS ID, shown in the right column of each row. In the example SLF table 210 illustrated in FIG. 2, a subscriber identified as “Fred@AOL.com” is mapped to HSS1 206A. Thus, if I-CSCF 202 needs to determine the location of Fred@AOL.com, it will first query SLF 208 to determine the appropriate HSS node 206, and then query the appropriate HSS node 206 to determine the identify of the switch that is serving Fred@AOL.com.
In the network illustrated in FIG. 2, I-CSCF 202 receives a SIP INVITE message 212 requesting a session with subscriber “Jenny@VZW.com”. To determine the current location of Jenny@VZW.com, I-CSCF 202 first queries SLF 208 to determine which HSS node 206 maintains location information for Jenny@VZW.com. I-CSCF 202 sends a Diameter location information request 214 to SLF 208, requesting location information for Jenny@VZW.com. SLF 208 responds with a Diameter redirect message 216, which instructs I-CSCF to redirect its LIR query to HSS2 206B. I-CSCF again issues a Diameter LIR query 218, this time to HSS2 206B, which issues a Diameter LIA response 220 back to I-CSCF 202. In the example illustrated in FIG. 2, HSS2 206B informs I-CSCF 202 that Jenny@VZW.com is being served by S-CSCF 204B. I-CSCF 202 forwards the SIP INVITE message, shown as SIP INVITE message 222, to S-CSCF 204B.
FIG. 3 is a block diagram illustrating an IMS network 300 having multiple HSS nodes. The functions of I-CSCF 202, S-CSCFs 204A and 204B, HSS nodes 206A and 206B, SLF 208, and SLF table 210 are essentially identical to their like-numbered counterparts in FIG. 2, and therefore descriptions of their functions will not be repeated here, with the exception of SLF 208. In network 300, SLF 208 does not redirect a Diameter LIR query but instead routes it to the appropriate HSS node 206 on behalf of I-CSCF 202.
Thus, in the network illustrated in FIG. 3, I-CSCF 202 receives a SIP INVITE message 302 requesting a session with subscriber “Jenny@VZW.com”. To determine the current location of Jenny@VZW.com, I-CSCF 202 first queries SLF 208 to determine which HSS node 206 maintains location information for Jenny@VZW.com. I-CSCF 202 sends a Diameter location information request 304 to SLF 208, requesting location information for Jenny@VZW.com. SLF 208 refers to SLF table 210 to determine that location information for Jenny@VZW.com is maintained at HSS2 2068, and sends or relays Diameter location information request 306 to HSS2 206B. HSS2 206B responds with a Diameter location information answer 308, which SLF 208 receives and forwards to I-CSCF 202. From Diameter location answer 208, I-CSCF 202 is informed that Jenny@VZW.com is being served by S-CSCF 204B. I-CSCF 202 forwards the SIP INVITE message, shown as SIP INVITE message 310, to S-CSCF 204B.
The networks illustrated in FIGS. 2 and 3, however, have no means to handle the situation where a mobile subscriber has been ported. FIG. 4 shows an example of a network that attempts to correct this disadvantage.
FIG. 4 is a block diagram illustrating another IMS network 400 having multiple HSS nodes. The functions of I-CSCF 202, S-CSCFs 204A and 204B, HSS node 206A, and SLF 208 are essentially identical to their like-numbered counterparts in FIG. 2, and therefore descriptions of their functions will not be repeated here, with the exception of SLF 208, which will be described in more detail below.
Network 400 includes a number portability database 402 for storing number portability information for subscribers. In the network illustrated in FIG. 4, I-CSCF 202 receives a SIP INVITE message 404 requesting a session with subscriber “9195551234”. To determine the current location of subscriber 9195551234, I-CSCF 202 sends a Diameter location information request 406 to SLF 208. SLF 208 may first check to see if subscriber 9195551234 has been assigned a new subscriber ID, by sending a subscriber ID map query (SMQ) 408 to, and receiving a subscriber ID map answer (SMA) 410 from, subscriber ID mapping database (SMDB) 402. If subscriber 9195551234 has been assigned a new subscriber ID, SMA 410 contains the new identifier allocated to subscriber 9195551234. SLF 208 then determines the HSS that serves the subscriber, and sends to I-CSCF 202 a Diameter redirect message 412 instructing I-CSCF 202 to redirect its Diameter location information request to an HSS node in the recipient network, such as HSS3 414.
In response to receiving Diameter redirect message 412, I-CSCF 202 issues Diameter location information request 416 to HSS3 414. HSS3 414 responds to I-CSCF 202 with a Diameter location information answer 418. From Diameter location information answer 418, I-CSCF 202 is instructed to forward the SIP INVITE message to a switch in the recipient network, SW_X 420. I-CSCF 202 forwards the SIP INVITE message, shown as SIP INVITE message 422, to recipient network switch SW_X 420.
There are disadvantages associated with the networks illustrated in FIGS. 1 through 4. Network 100 does not contain multiple HSS nodes. Network 200 contains multiple HSS nodes, but requires the I-CSCF to make two queries: one to determine the correct HSS node, and the second to get information from the correct HSS node. Network 300 allows the I-CSCF to make one query, but has no means to deal with ported subscribers. Network 400 checks for ported subscribers, but again forces the I-CSCF to make two queries: if the subscriber is ported, the SLF instructs the I-CSCF to ask another HSS for information.
Another issue involves technology migration, such as where a subscriber has migrated from one network standard or protocol to another network standard or protocol. For example, in mixed 2G/3G/SIP/IMS networks, what was formerly a 2G subscriber may upgrade to a 3G device or want to access the network using a SIP-capable terminal. This may happen because a subscriber has changed network service providers (and is also likely to be a number portability candidate), but this may also happen as a network provider supports more, different, or better telecommunications standards. In a technology migration scenario, a subscriber whose information was formerly maintained by an HLR, for example, may now have that information maintained at an HSS. The networks described above have no means to check for this scenario.
Accordingly, in light of these potential disadvantages, there exists a need for methods, systems, and computer readable media for providing a home subscriber server (HSS) proxy.